1. Field
Embodiments of the present invention relate to a method of setting valid output sections of a 2-axis acceleration sensor or a 3-axis acceleration sensor which sets precise valid sections applied to detect information between a tire and a ground surface from output signals from a multi-axis (2-axis or 3-axis) acceleration sensor mounted within the tire.
2. Description of the Related Art
In general, an acceleration sensor means a device which measures dynamic force, such as acceleration, vibration, impact, etc. of an object, by processing an output signal. Such an acceleration sensor may precisely sense the moving state of the object, and thus an application range thereof is increasingly widened for various purposes. The acceleration sensor is essential in various transport units, such as vehicles (automobiles), ships, airplanes, etc., factory automation systems and control systems of robots.
Particularly, a 3-axis acceleration sensor is used in a vehicle collision test and an air bag development test. In order to obtain a desired test result from a vehicle in such tests, a test process is commonly repeated several hundred times or more.
Further, the 3-axis acceleration sensor used in these tests is a sensor to simultaneously measure accelerations varied in the x-axis, y-axis and z-axis directions, i.e., to obtain rates of change of velocity for the respective axes. Here, the measured acceleration is a value obtained by dividing change of velocity by unit time, i.e., means change of the velocity of a moving object per unit time, and the acceleration sensor changes a quantity of a motion, such as the velocity, the acceleration, etc. of a moving object, into a constant value (voltage), thereby serving to measure the velocity, the acceleration, etc.
Therefore, acceleration sensors have been widely used in a vibration test and a durability test of an object, a fatigue test, a collision test, an air bag development test and various other fields, and thus science technology development is not expected without acceleration sensors.
In general, a 3-axis acceleration sensor is attached to a rotating wheel to measure the acceleration of the wheel, and vibration or shaking of the wheel is tested using the measured value. As acceleration sensors, a wired type and a wireless type are used, and the wireless type is very expensive and thus the wired type is most commonly used.
If a multi-axis (3-axis) acceleration sensor is mounted within a tire, when impact from the outside is applied to the tire, the acceleration sensor outputs a result, and information between the tire and the ground surface is judged from output characteristics represented when the part of the tire where the acceleration sensor is mounted contacts the road surface. Due to characteristics in which the multi-axis acceleration sensor is mounted within the tire, the information between the tire and the ground surface may be precisely detected when external input (impact) is continuously applied to the tire during driving of a vehicle and external input applied from other regions than the ground surface is treated as a noise component.
Conventionally, a method in which information of a tire and a ground surface is judged respectively using output characteristics of the 3-axis acceleration sensor in the x-axis, y-axis and z-axis directions is applied. However, when the 3-axis acceleration sensor is applied to an actual test, a severe noise component is added to an output signal of the acceleration sensor, and thus it may be difficult to detect valid output sections of the sensor respectively using the output characteristics of the sensor in the x-axis, y-axis and z-axis directions.